Fig 3.

Frequency of antigen-specific IFN-γ-secreting T lymphocytes present at the time of M. bovis challenge. At 12 months (BCG 12) or 24 months (BCG 24) post-BCG vaccination, memory cell responses were assessed by cultured ELISPOT. The responses in control animals were also assessed: these were not significantly different at either time point, and the data were therefore pooled for analysis. The number of PPD-B-specific IFN-γ SFC present within PBMC was significantly higher in vaccinated animals at 12 months, but not at 24 months, postvaccination, compared with control, nonvaccinated animals. Mean ± standard deviations are shown (n = 9 for vaccinated groups; n = 18 for controls). *, P < 0.05.